Flushing valve arrangement for reversible hydrostatic gear mechanisms

ABSTRACT

A flushing valve arrangement for reversible hydrostatic gear mechanisms with a closed circuit and a feed pump which communicates through non-return valves with each of two main lines of the circuit and with a pressure relief valve connected to a storage container. Its inlet can, through a flushing reciprocating valve and as a function of the pressure in the relevant high pressure line, communicate with whichever main line is carrying the low pressure. The flushing reciprocating valve comprises two coaxially and mirror-symmetrically disposed valve bodies enclosing a common valve space which communicates with said pressure relief valve, said valve bodies having within them displaceable and likewise mirror-symmetrically disposed piston slides reciprocally braced through a spring between said slides. Each piston slide has an inner valve space communicating with the common valve space and with the feed pump. Each valve body with its associated piston slide by means of a sealing piston face and a valve seat forms an annular space which can be closed off from the common valve space and which communicates at any time with one of the main lines. Each main line is connected through a control valve to a control space on the outer end face of the other piston slide which forms an annular space connected to the other main line.

United States Patent 1191 Sirek 1 51 May 1, 1973 FLUSHING VALVEARRANGEMENT [57] ABSTRACT FOR REVERSIBLE HYDROSTATIC A flushing valvearrangement for reversible hydro- GEAR MECHANISMS static gear mechanismswith a closed circuit and a {75] Inventor; Tomas Sirek, Hausen, Germanyfee pump which communicates through non-return [73] Assigneez ConstantinRauch p Donau Lis valves with each of two main lines of the circuit andtrasse, Germany with a pressure relief valve connected to a storagecontainer. Its inlet can, through a flushing reciprocat- Filedi 1971 ingvalve and as a function of the pressure in the rele- [211 App] No:203,522 vant high pressure line, communicate with whichever main line iscarrying the low pressure. The flushing reciprocating valve comprisestwo coaxially and mir- Foreign Application Priority Dataror-symrnetrically disposed valve bodies enclosing a Dec. 17, 1970Germany ..P 20 62 308.9 common valve space which communicates with Saidpressure relief valve, said valve bodies having within 52 US. Cl...l37/87, 60/52 B, 60/53 R, them displdcwble and likewisemirror-symmetrically 137/110 137/119 disposed piston slides reciprocallybraced through a 51 Int. Cl ..Fl6d 31/00 p g between d slides- Eachpiston slide has an 58 Field of Search ..l37/87, 109, 110, inner valvespace communicating with the 99mm 137/1 18, 119; 60/52 B, 53 R valvespace and with the feed pump. Each valve body with its associated pistonslide by means of a sealing [56] References Cited piston face and avalve seat forms an annular space which can be closed off from thecommon valve space UNITED STATES PATENTS 1 and which communicates at anytime with one of the 2,069,366 2/1937 Heerdt ..137 109x main E3611 mainline is Connected through 8 2,122,045 6/1938 Rose et alm. ..l37/87 Xcontrol valve to a control space on the outer end face 2,961,829 11/1960Weisenbach. ....60/53 R of the other piston slide which forms an annularspace 3,507,298 4/1970 Ratliff ....60/53 R onnected to the other mainline, 3,561,214 2/1971 Bob'st ..6()/53 R 5-Claims, 1 Drawing FigureFLUSHING VALVE ARRANGEMENT FOR REVERSIBLE HYDROSTATIC GEAR MECHANISMSstorage container. The input of the pressure relief valve is connectablethrough a flushing reciprocating valve and, as a function of thepressure in the particular high pressure line concerned, to whichevermain line is carrying the low pressure.

Such valve arrangements are intended to feed fresh oil constantly to thecircuit in order to replace oil losses and to replace the hot circuitoil continuously for cooled fresh oil. Furthermore, they are intendedboth to maintain the feed pressure at a definite level and to restrictthe circuit pressure.

In an arrangement of the aforementioned type, a feeding filler pump isconnected through non-return valves to the main lines and, connected toa storage container is a low pressure relief valve, the inlet of whichis connected through a reciprocating valve to whichever main linecarries the low pressure. The reciprocating valve is reversed by thedifferential pressure in the two main lines. A high pressure reliefvalve is provided whose input is connected to whichever main line iscarrying the high pressure (DAS l 400 668). The reciprocating valve alsohas connecting apertures and control grooves, through which the mainline carrying the high pressure is connected to the high pressure reliefvalve, the outlet of which discharges into the inlet of the low pressurerelief valve. With this arrangement, a special high pressure limitingvalve is provided which must be designed for the full output of the highpressure circuit. In addition, where this known arrangement isconcerned, an additional low pressure valve is required so that, in theneutral position of the reciprocating valve, it is possible to draw offthe filling oil being passed by the filler pump.

In the case of another known arrangement, the last mentioned additionallow pressure valve is not required, because a direct connection isprovided between the feed pump and the pressure relief valve via theflushing arrangement, i.e., the reciprocating valve. However, this knownarrangement does not act as a pressure limiting valve for the highpressure circuit so that additional high pressure valves and/orreversing valves would be required.

One general object of the present invention is to solve the problem ofproviding a valve arrangement of the aforementioned type that will serveat the same time as a pre-control high pressure limiting valve so thatthe flushing process will not be interrupted.

In general this problem is solved by a flushing reciprocating valvecomprising two coaxially and mirror-symmetrically disposed valve bodieswhich enclose a common valve space that communicates with a pressurerelief valve and within these bodies are displaceable,mirror'symmetrical piston slides which are braced with respect to eachother through a spring, each slide having an inner valve spacecommunicating with the common valve space, the inner valve spacecommunicating with the feed pump. Each valve body, with its associatedpiston slide and by means of a sealing piston surface and a valve seat,forms an. annular space which can be closed off from the common valvespace and which communicates in each case with one of the main lines.Each main line is connected through a control valve to a control spaceon the outer end of the other piston slide, which forms the annularspace connected to the other main line.

It is already known (U.S. Pat. No. 2,122,045) in the case of areversible hydrostatic gear mechanism with a closed circuit, to providea reciprocating valve which connects the main line carrying the lowpressure with a feed pressure line, according to the pressure in therelevant high pressure line, in order to make up leakage oil losses inthe mechanism. The reciprocating valve likewise has two coaxially andmirror-symmetrically disposed piston slides, a common valve spacelocated between the two piston slides being connected to the feed pump.However, here this valve space is connected directly to whichever mainline is carrying the low pressure.

When an inadmissible pressure arises in the high pressure line of thegear mechanism, the piston slide associated with the high pressure linelifts off its seating against the initial tension of a spring whichurges the two piston slides towards each other, pressing them onto aseating. This connects the high pressure line to the valve space of theswinging valve and thus to the low pressure line. Where the known gearmechanism is concerned, a flushing valve is not provided, so thatflushing in any stage of operation is not possible.

The construction of the present arrangement offers the decisiveadvantage that it serves at the same time as a pressure limiting valvefor the high pressure circuit without a special high pressure limitingvalve, which would need to be designed for the full output of the highpressure circuit, being provided. Only a control valve designed forlesser output, possibly corresponding to the output of the feed circuit,need be provided. The design of the arrangement is such that theflushing process isnot interrupted even if there is a response tooverpressure in the high pressure circuit. Thus, the flushing valvearrangement proposed is particularly suitable for gear mechanisms ofhigh output.

In an advantageous further development of the invention, after the forceof the spring bracing the piston slide has been overcome, the facinginner ends of the piston slides bear sealingly on each other, separatingthe inner valve spaces from the common valve space. The design of thebracing spring will generally be such that the piston slides bear insealing-tight manner on each other when maximum possible flushing is tobe achieved.

To this end, in a further development of the invention, the inner valvespaces of the piston slides communicate with the feed pump through anaperture which, in the neutral position of each piston slide, alignswith a connecting aperture for a feed line in the valve body. Inconsequence, at maximum flushing, the entire quantity of feed oil is fedthrough the non-return valve into the main line of the circuit which isat that time carrying low pressure.

Other objects, advantages and features of the present invention willbecome apparent from the following detailed description of an exemplaryembodiment of the invention as will be explained in greater detailhereinafter with reference to the attached drawing, which is a partiallydiagrammatic view in section of a flushing valve arrangement accordingto the present invention.

Referring to the drawing, a valve housing 6 has a continuous cylindricalbore into which, from each end, a valve body 7, 7 can be inserted andsecured by means of a screw 8, 8'. In the valve bodies 7, 7' slidemirror-symmetrical slides 9, 9' which, in the region of their facinginner ends, have a sealing piston face ll, 11 and which are braced withrespect to each other through a spring 10. The piston faces 11, 11' bearon valve seats 12, 12' constructed in the valve bodies 7, 7'. Thus, twoannular spaces 13, 13' are formed which are connected on the other handto the main lines 4, 4' and on the other, through control valves 18, 18to control spaces 15, 15 on the remote outer end spaces of the otherpiston slide 9 9. The control valves 18, 18' are constructed asthree-way throttle valves which are adjustable by the supply pressureand which, from the moment of reaching a predetermined pressure in thehigh pressure circuit or in the main line 4, 4, start to close. Theoutflow connections of the control valves 18, 18' communicate with innervalve spaces 17, 17 which are formed in the piston slides 9, 9'. Feedlines 2, 2' discharge into these valve spaces 17, 17. The inner valvespaces 17, 17 communicate through the facing sides of the piston slides9, 9 with the common valve space 16 which in turn connects with the feedpressure valve which again discharges into the storage container l9.Situated downstream of the feed pump 1 are filters 20 and a coolingmeans 21, from which the feed oil can pass through the feed lines 2, 2,through nonreturn valves 3, 3' into the low pressure main line 4, 4'.The feed lines 2, 2 discharge thereby into the low pressure main line 4,4 at a place which, in the direction of flow of the oil, is located inthe line and downstream of the connection of the feed pressure valve 5or the annular spaces 13, 13 (a place which is not shown in thedrawing). This guarantees that the entire quantity of flushing oil fedin is supplied to the circuit, after the heated oil has been discharged4 which happens by the backwash of old oil against the fresh (flushing)oil.

The valve arrangement operates in the following way:

1. As long as there is no difference in pressure in the cricuit and thusin the main lines, 4, 4', the flushing reciprocating valve or the twopiston slides 9, 9' remain in the position shown in the drawing. Whilethis is so, the oil passed by the feed pump 1 out of the storagecontainer 19 through the feed lines 2, 2', via the nonreturn valves 3,3, will replace the leakage oil losses in the circuit. The excessquantity of feed oil flows through the feed lines 2, 2', the connectingapertures 22, 22' and the apertures 14, 14' in the piston slides 9, 9'to the inner valve spaces l7, l7 and from there to the common valvespace 16 and the feed pressure valve 5 back into the storage container19.

2. If the pressure rises for example in the main line 4, then theassociated non-return valve 3 closes. The increased pressure acts on thepartial surface of the sealing piston face 11 which is limited by theseat 12 in the valve space 13 and acts at the same time through thefully opened throttle 18 in the control space The t and scope of theinvention. The disclosures and the effective piston area in the controlspace 15' is dimensioned larger than the described partial area of thepiston face 11 in the valve space 13, so that the piston slide 9' movesrightwards until equilibrium is established with the force of the spring10. The valve formed by piston face 11 and seat 12 remains closedthereby. The valve formed between the piston face 11' and the seat 12'is continuously opened during the process described and flushing takesplace by the drawing of oil from the circuit into the common valve space16 and from there through the feed pressure valve 5 into the storagecontainer 19.

3. With effect from a high pressure in the main line 4 which isdetermined by the construction of the Spring 10 so the piston slide 9'has its inner end face bearing in sealing-tight manner on the inner endface of the piston 9. Thus, the inner valve spaces l7, 17 are connectedto each other and separated from the valve space 16, so that the entirequantity of feed oil is passed by the feed pump 1 through the non-returnvalve 3' into the main line 4 which is carrying the low pressure.

4. If, in the main line 4, the maximum pressure adjusted by the responsepoint of the control valve or the throttle 18 is exceeded, then thethrottle 18 starts to close and lowers the pressure in the controlchamber 15'. Thus, the pressure acting on the partial area of the pistonface 1 1 of the piston slide 9 in the valve chamber 13 predominates andlifts the piston face 1 1 off the seat 12. With this, the piston 9 andthe piston 9' which in this condition bears on it in sealing-tightmanner take over as one unit the function of a pressure limiting valve.The oil which is thereby splashed into the valve face 16 from thecircuit is discharged through the feed pressure valve 5 in the storagecontainer 19, so long as the quantity of fed-in feed oil is notexceeded. If the quantity is exceeded, the excess part of the oil flowsthrough the opened valve which is formed between the piston face 11' andthe seat 12' and into the main line 4' which is carrying the lowpressure.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit description herein are purely illustrative and are notintended to be in any sense limiting.

I claim:

1. In a flushing valve arrangement for reversible hydrostatic gearmechanisms with a closed circuit and a feed pump which communicatesthrough non-return valves with each of the two main lines of thecircuit, and with a pressure relief valve connected to a storagecontainer and of which the inlet can, through a flushing reciprocatingvalve and as a function of the pressure in the relevant high pressureline, communicate with whichever main line is carrying the low pressure,the improvement wherein the flushing reciprocating valve comprises twocoaxially and mirror-symmetrically disposed valve bodies enclosing acommon valve space which communicates with said pressure relief valve,said valve bodies having within them displaceable and likewisemirror-symmetrically disposed piston slides reciprocally braced througha spring between said slides, each said slide having an inner valvespace communicating with the common valve space and with the feed pump,each said valve body with its associated piston slide, by means of asealing piston face and a valve seat, forming an annular space which canbe closed off from the common valve space and which communicates with atany time one of the main lines, each main line being connected through acontrol valve to a control space on the outer end face of the otherpiston slide which forms an annular space connected to the other mainline.

2. The flushing valve arrangement according to claim 1 wherein the forceof the spring which braces the piston slides is such that when it hasbeen overcome, the facing inner ends of the piston slides bear on eachother in sealing-tight manner, separating the inner valve spaces fromthe common valve space.

3. The arrangement according to claim 2 wherein the inner valve spacesof the piston slides are connected to the feed pump through an aperturewhich, in the neutral position of each piston slide, aligns with aconnecting aperture for a feed line in the valve body.

4. The arrangement according to claim 3 wherein said control valves arethree-way throttle valves which are adjustable by the supply pressure,their outflow connection being connected to said inner valve space of.the associated piston slide.

5. The arrangement according to claim 3 wherein the inflow aperture ofeach said control valve is connected to said annular space of theassociated piston slide.

1. In a flushing valve arrangement for reversible hydrostatic gearmechanisms with a closed circuit and a feed pump which communicatesthrough non-return valves with each of the two main lines of thecircuit, and with a pressure relief valve connected to a storagecontainer and of which the inlet can, through a flushing reciprocatingvalve and as a function of the pressure in the relevant high pressureline, communicate with whichever main line is carrying the low pressure,the improvement wherein the flushing reciprocating valve comprises twocoaxially and mirrorsymmetrically disposed valve bodies enclosing acommon valve space which communicates with said pressure relief valve,said valve bodies having within them displaceable and likewisemirrorsymmetrically disposed piston slides reciprocally braced through aspring between said slides, each said slide having an inner valve spacecommunicating with the common valve space and with the feed pump, eachsaid valve body with its associated piston slide, by means of a sealingpiston face and a valve seat, forming an annular space which can beclosed off from the common valve space and which communicates with atany time one of the main lines, each main line being conneCted through acontrol valve to a control space on the outer end face of the otherpiston slide which forms an annular space connected to the other mainline.
 2. The flushing valve arrangement according to claim 1 wherein theforce of the spring which braces the piston slides is such that when ithas been overcome, the facing inner ends of the piston slides bear oneach other in sealing-tight manner, separating the inner valve spacesfrom the common valve space.
 3. The arrangement according to claim 2wherein the inner valve spaces of the piston slides are connected to thefeed pump through an aperture which, in the neutral position of eachpiston slide, aligns with a connecting aperture for a feed line in thevalve body.
 4. The arrangement according to claim 3 wherein said controlvalves are three-way throttle valves which are adjustable by the supplypressure, their outflow connection being connected to said inner valvespace of the associated piston slide.
 5. The arrangement according toclaim 3 wherein the inflow aperture of each said control valve isconnected to said annular space of the associated piston slide.